1.SELECT D_PAY, N_PAYMENT, (SELECT N_DEBT
                          FROM computation
                          WHERE D_COMPUTATION = (SELECT MAX(D_COMPUTATION)
                                                 FROM computation
                                                 WHERE D_COMPUTATION <= pay.D_PAY)
                          AND N_CLIENT = pay.N_CLIENT) debt
FROM payment pay
WHERE N_CLIENT = (SELECT N_CLIENT
                  FROM computation
                  WHERE N_DEBT = (SELECT MAX(N_DEBT)
                                  FROM computation))




2.select rownum rn, (select round( avg(pcom.n_sum_cold),2)
                   from computation pcom
                   where pcom.n_client = com.n_client) sumcold,
                  (select round( avg(pcom1.n_sum_hot),2)
                   from computation pcom1
                   where pcom1.n_client = com.n_client) sumhot

from
   (select com1.n_client
    from computation com1
    order by n_info_cold desc) com
where rownum  < 11




3.select *
 from
     (SELECT C_STREET, COUNT(client.N_CLIENT) cnt
      FROM client, street
      WHERE client.N_STREET = street.N_STREET
      GROUP BY street.C_STREET)
where cnt=(select max(cnt)
           from
          (SELECT C_STREET, COUNT(client.N_CLIENT) cnt
           FROM client, street
           WHERE client.N_STREET = street.N_STREET
           GROUP BY street.C_STREET))

4.select rownum rn, (select 'г.' ||  city.c_city || ' ул.' || street.c_street || ' д.' || client.c_house || ' кв.' || client.n_flat
                   from client,city,street
                   where city.n_city = client.n_city
                   and street.n_street = client.n_street
                   and client.n_client = com.n_client) address

from
   (select com1.n_client
    from computation com1
    order by n_info_cold desc) com
where rownum  < 11

5.SELECT to_char(payment.d_pay,'MM'), sum(payment.n_sum)
FROM   payment
WHERE  payment.d_pay > (SELECT min(payment.d_pay)
                       FROM payment
                       where payment.n_sum = (SELECT MAX(n_sum)
                                                        FROM payment))
group by to_char(payment.d_pay,'MM')


6.SELECT client.c_last_name, client.c_first_name, client.c_second_name, city.c_city, street.c_street, client.c_house, client.n_flat, computation.n_debt
from city, street, client, computation
WHERE client.n_city = city.n_city
AND client.n_street = street.n_street
AND client.n_client = computation.n_client
AND computation.n_debt = (SELECT MIN(n_debt)
                          from computation)


7.select clnt.C_First_Name,clnt.C_Second_Name, clnt.C_Last_Name, pay.d_pay, pay.n_sum
    from payment pay,client clnt
    where pay.n_client=clnt.n_client
    and pay.n_sum = (select max(pay1.n_sum)
                        from payment pay1
                      )